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ECG: Myths and facts

The ECG is an indispensable tool but there are many wrong ideas about its use.

MILLIONS of people undergo the electrocardiogram (ECG) and the procedure has saved lives of innumerable patients by showing a serious condition like heart attack with a fair degree of accuracy. It is almost synonymous with a lifeline, as death is diagnosed when the ECG recording shows no activity or a straight line. Despite the progress made in cardiac investigation and development of sophisticated gadgets in cardiology, the ECG remains absolutely invaluable and unavoidable in cardiac assessment.

Misconceptions

However there are many wrong ideas, misconceptions and myths about the use and interpretation of ECG. These create a lot of problems for both doctors and patients. The problem has been compounded by the modern computerised machines, which give reports instantly typed on the ECG itself. Unfortunately, these reports are either wrong or misleading in about 30 to 40 per cent of the cases. This is because of the several parameters that influence the ECG - age, gender, race, clinical condition, blood electrolyte levels, not to speak of the other factors that frequently occur in the recordings). These parameters are not given as inputs into the computer nor are reporting programmes perfect enough to take into consideration the many variable parameters that influence the ECG. However, in clinical cardiology ECG is absolutely indispensable and very valuable because in certain conditions like arrhythmia, bundle branch block, heart block, certain types of ischaemic heart disease or infarction the abnormalities if seen are almost diagnostic. Nonetheless a normal ECG does not rule out disease or abnormalities in the heart. Myth: If ECG is normal the heart is normal. Fact: Nothing could be more wrong. ECG could be normal in the presence of serious heart disease and vice versa. Myth: ECG is superior to clinical examination and assessment by the doctor. Fact: ECG is only complementary or supportive to the doctor's clinical diagnosis. Myth: Echocardiogram has replaced the value and use of ECG.Fact: Not at all. ECG gives information about the electrical activity of the heart whereas the echocardiogram gives information about the structural or anatomical aspects of the heart. Myth: In serious heart diseases ECG must show abnormality.Fact: Not so. In the presence of some serious heart disease ECG could still be normal. Myth: If the ECG is abnormal the person must be having some heart disease.Fact: Not so always. There are many non-specific, normal variations in the ECG waves and segments, which are neither diagnostic nor indicative of any abnormal condition. Myth: ECG can indicate heart failure or heart attack. Fact: Neither. Heart failure is a failure of satisfactory contraction of the muscles of the heart in relation to demand, which is not reflected in the ECG. In 50 per cent of heart attacks also the ECG may be normal in the beginning for some time or in some unusual locations of the areas of the heart attack (Myocardial Infarction).Myth: ECG diagnosis is purely objective and therefore there is no interpersonal variation in its interpretation. Fact: Not correct. Proper interpretation of the ECG depends on the skill, training and experience of the interpreter as well as the correlation with the clinical diagnosis as some abnormalities in the ECG could be present in both normal variations and abnormal conditions of the heart. ECG is to be always correlated with the clinical diagnosis and be interpreted by an experienced physician.It is therefore important to appreciate the myths and facts about this simple, common and totally indispensable tool in cardiac investigation. It is in the patients' and doctors' interest that this should be widely known to the public. The author is a senior cardiologist and is the President of the Indian Society of Electrocardiology.